Model Forum / Radio Controlled / Air Models / May 2007

I have a true float charger for my sailplane winch battery. It says it
switches to float mode when the battery is charged. Looking at the
charts it drops back to 2.15 vdc per cell when in float mode and it is
2.35 vdc (or more) in charge mode. I doubt you need to worry about
battery sulfation for the short periods that you charge in the field. Is
your field battery a sealed gel type or a wet motorcycle or lawn tractor
type?

Stefan-

Float chargers put out a small constant current that is intended to
make up for the normal self-discharge of wet or gel cell batteries
during storage or infrequent use.  It has the advantage of maintaining
charge without boiling off the electrolyte, as the usual rapid
chargers do when left connected for extended periods.  It's a trade
off - I am using a 17AH gel cell that was salvage from a motorized
bicycle factory that tanked, and the float charger keeps it ready for
as often as I use it for charging R/C and E-flite batteries, a couple
of times a week. The advantage is the operation is set it up and
forget it.  Easier than using a normal Pb battery charger that needs
to be turned on periodically to recharge the gell cell.  OTOH, it
wouldn't work well under the demands of a greater duty cycle.
Actually, I keep in the garage where it is convenient for charging
batteries in larger models I don't want to lug to the shop, and use a
workhorse 20 A benchtop power supply in my shop for most charging. The
$15 gel cell battery and $5 (at Harbor Freight) float charger make a
power supply for R/C chargers at a price that's hard to beat, though.
Oh, your charger with the green LED is not likely a float charger, as
the float charger's job is never done - they charge continuously at
the same rate until disconnected from the AC source.

Abel